Cyclopropenoid fatty acids (CPFA) which occur in certain foodstuffs such as cottonseed oil and flour, kapok oil and okra are known to have toxic effects when consumed by animals. In addition, our studies have demonstrated that CPFA acts as powerful promoting agents or cocarcinogens for aflatoxin induced liver cancer in rainbow trout. This research shall have as the primary goals an explanation for the cocarcinogenic activity of CPFA, and to further our knowledge of their toxic effects in trout and rats. The chemical synthesis of CPFA, C14 labelled compounds, and cyclopropene derivatives will be an important objective for this study. The structural specificity required for cocarcinogenesis will be determined and the metabolic fate of CPFA as well as the accumulation by prenatal and postnatal animals will be investigated. CPFA, which are known to inhibit certain enzyme systems, will be investigated for possible effects on nucleic acid metabolism and protein synthesis.